Verify that a table is empty, and add it to replication.
tab_idxname is optional - if NULL, then we use the primary key.
Note that this function is to be run within an EXECUTE SCRIPT script,
so it runs at the right place in the transaction stream on all
nodes.

declare
p_set_id alias for $1;
p_tab_id alias for $2;
p_nspname alias for $3;
p_tabname alias for $4;
p_idxname alias for $5;
p_comment alias for $6;
prec record;
v_origin int4;
v_isorigin boolean;
v_fqname text;
v_query text;
v_rows integer;
v_idxname text;
begin
-- Need to validate that the set exists; the set will tell us if this is the origin
select set_origin into v_origin from sl_set where set_id = p_set_id;
if not found then
raise exception 'add_empty_table_to_replication: set % not found!', p_set_id;
end if;
-- Need to be aware of whether or not this node is origin for the set
v_isorigin := ( v_origin = getLocalNodeId('_schemadoc') );
v_fqname := '"' || p_nspname || '"."' || p_tabname || '"';
-- Take out a lock on the table
v_query := 'lock ' || v_fqname || ';';
execute v_query;
if v_isorigin then
-- On the origin, verify that the table is empty, failing if it has any tuples
v_query := 'select 1 as tuple from ' || v_fqname || ' limit 1;';
execute v_query into prec;
GET DIAGNOSTICS v_rows = ROW_COUNT;
if v_rows = 0 then
raise notice 'add_empty_table_to_replication: table % empty on origin - OK', v_fqname;
else
raise exception 'add_empty_table_to_replication: table % contained tuples on origin node %', v_fqname, v_origin;
end if;
else
-- On other nodes, TRUNCATE the table
v_query := 'truncate ' || v_fqname || ';';
execute v_query;
end if;
-- If p_idxname is NULL, then look up the PK index, and RAISE EXCEPTION if one does not exist
if p_idxname is NULL then
select c2.relname into prec from pg_catalog.pg_index i, pg_catalog.pg_class c1, pg_catalog.pg_class c2, pg_catalog.pg_namespace n where i.indrelid = c1.oid and i.indexrelid = c2.oid and c1.relname = p_tabname and i.indisprimary and n.nspname = p_nspname and n.oid = c1.relnamespace;
if not found then
raise exception 'add_empty_table_to_replication: table % has no primary key and no candidate specified!', v_fqname;
else
v_idxname := prec.relname;
end if;
else
v_idxname := p_idxname;
end if;
return setAddTable_int(p_set_id, p_tab_id, v_fqname, v_idxname, p_comment);
end